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PMID:19545236

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Citation

Cailliatte, R, Lapeyre, B, Briat, JF, Mari, S and Curie, C (2009) The NRAMP6 metal transporter contributes to cadmium toxicity. Biochem. J. 422:217-28

Abstract

NRAMP (natural resistance-associated macrophage protein) homologues are evolutionarily conserved bivalent metal transporters. In Arabidopsis, AtNRAMP3 and AtNRAMP4 play a key role in iron nutrition of the germinating plantlet by remobilizing vacuolar iron stores. In the present paper we describe the molecular and physiological characterization of AtNRAMP6. AtNRAMP6 is predominantly expressed in the dry seed embryo and to a lesser extent in aerial parts. Its promoter activity is found diffusely distributed in cotyledons and hypocotyl, as well as in the vascular tissue region of leaf and flower. We show that the AtNRAMP6 transcript coexists with a partially spliced isoform in all shoot cell types tested. When expressed in yeast, AtNRAMP6, but not its misspliced derivative, increased sensitivity to cadmium without affecting cadmium content in the cell. Likewise, Arabidopsis transgenic plants overexpressing AtNRAMP6 were hypersensitive to cadmium, although plant cadmium content remained unchanged. Consistently, a null allele of AtNRAMP6, named nramp6-1, was more tolerant to cadmium toxicity, a phenotype that was reverted by expressing AtNRAMP6 in the mutant background. We used an AtNRAMP6::HA (where HA is haemagglutinin) fusion, shown to be functional in yeast, to demonstrate through immunoblot analysis of membrane fractions and immunofluorescence localization that, in yeast cells, AtNRAMP6 is targeted to a vesicular-shaped endomembrane compartment distinct from the vacuole or mitochondria. We therefore propose that AtNRAMP6 functions as an intracellular metal transporter, whose presence, when modified, is likely to affect distribution/availability of cadmium within the cell.

Links

PubMed Online version:10.1042/BJ20090655

Keywords

Amino Acid Sequence; Arabidopsis/chemistry; Arabidopsis/drug effects; Arabidopsis Proteins/chemistry; Arabidopsis Proteins/metabolism; Base Sequence; Cadmium/toxicity; Cadmium Poisoning/metabolism; Cation Transport Proteins/chemistry; Cation Transport Proteins/metabolism; Molecular Sequence Data; Plant Leaves/chemistry; Plant Leaves/drug effects

Significance

Annotations

Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status

ARATH:NRAM6

enables

GO:0015086: cadmium ion transmembrane transporter activity

ECO:0000314: direct assay evidence used in manual assertion

F

Seeded From UniProt

complete

ARATH:NRAM6

involved_in

GO:0070574: cadmium ion transmembrane transport

ECO:0000314: direct assay evidence used in manual assertion

P

Seeded From UniProt

complete


See also

References

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